Following the surgical removal of a hollow vessel portion, e.g. with an intestinal resection due to a tumor having affected a bowel section, the two hollow vessel portions have to be reconnected at their opened ends in such a manner that a continuous pathway is produced. This is referred to as end-to-end anastomosis. As a standard, the two opened ends are reattached to each other with clip suturing devices.
In particular with operations on the small and large intestines, leaky suture connections (suture insufficiency) occur from time to time, which are associated with a serious progress of disease and a high mortality rate, too.
An alternative to stitching the hollow vessel portions is thermofusion technology (TFT). Thermofusion by means of high frequency technology (HF) is based on the denaturation of proteins which are contained in many tissue types. This allows to weld collagen-containing tissue. During the welding process, the tissue is heated up to temperatures above the protein denaturation temperature, and together with the intra- and extracellular matrix is converted into a gel-like state. After compression of the tissue faces, the liquefied tissue cools down to a fused mass, effecting a reliable connection of the tissue.
For the purpose of welding the hollow vessel portions, the tissue grasped between two clamping jaws is exposed to electrical current which flows between electrodes provided on the two clamping jaws.
For preventing the sealing or welding from breaking down, the parameters acting on the tissue have to be detected and controlled. In order to ensure this, a precise control of temperature, pressure, tissue impedance, distance and position is required.
It is desirable to realize a uniform treatment of the tissue which is held between the clamping jaws, so that all regions are reliably reached and no region is exposed to an excessively high current. To this end, it has to be ensured that the HF electrodes are uniformly spaced from each other and aligned so as to be parallel to each other.
The prior art does not disclose any instruments of suitable size for being used for the above-mentioned hollow vessels and tissue types. Coagulation instruments of smaller size, as shown e.g. in EP 1 747 762 A2, exhibit a nonparallel alignment of the HF electrodes during closing the clamping jaws, which is due to the construction.
The distance between the electrodes can be maintained by spacers mounted on the clamping jaws. If, however, a larger number of spacers is provided on the clamping jaws, as is shown e.g. in EP 1 656 901 B1, EP1 952 777 A1, EP 1 372 507 A1 or US 2004/122423 A1, it is inevitable that the spacers perforate the tissue to be treated, as the tissue is compressed under the spacers with closed clamping jaws in such a manner that permanent damages on the tissue will occur. This has negative effects on the result of the sealing process.
If the contact pressure of the clamping jaws is reduced in order to avoid perforation of the tissue, and the tissue is only clamped underneath the spacers, this will result in an angular deflection of the clamping jaws.
As the spacers are further made from an electrically non-conductive material for avoiding a short-circuit between the HF electrodes, a so-called coagulation shade develops in the vicinity of said spacers, which means that the tissue portions are encapsulated in the vicinity of or under the spacers, hence are not supplied with electrical current or only to an insufficient extent, and an unsatisfactory welding of the vessel portions will be produced. Furthermore, it has turned out that electrically insulating spacers of this type may readily flake off, in particular in case they are attached to the electrode e.g. by gluing, with the risk that they may find their way into the patient body possibly even unnoticed. In addition to that, the predefined electrode spacing is not ensured any more.
Against this background, the present invention is based on the object to provide an instrument which improves, by means of thermofusion technology, the result of an end-to-end anastomosis of hollow vessels such as small and large intestines or, in general, improves the result with tissue connections, ensures in particular a parallel alignment of the HF electrodes without any damage on the tissue, and has an improved functional reliability.